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Monday, April 06, 2009

What the heck could increased variation in red blood cell size have to do with heart disease or mortality?

This article from the Archives of Internal Medicine seems to link a measure of variability in red blood cell (rbc) size with all cause mortality. As the article explains, previously there had several studies that suggested a link between heart disease and RBC size variability as judged by measurement of the RDW by automated blood cell analyzers. (See here for one article linking elevated RDW and adverse clinical outcomes in patients with heart disease). The Archive article examined a large data base for evidence of a similar correlation with all cause mortality and seemed to find one that reached statistical significance.

The RDW is the red cell distribution width which is the standard deviation of red cell width divided by the mean cell width and normally is around 10-15 %. Remember we used to talk about anisocytosis. It may have some limited utility in differentiating iron deficiency anemia from thalassemia with the RDW increased in the former reflecting the fact that in iron deficiency there are two populations of red cells and in thalassemia there is a more homogeneous population of relatively small rbcs. In my experience, it is a by product of automatic blood cell analyzers that most docs ignore, including a couple of hematologist associates I asked about it.

The study authors also wondered how/why RDW seems to correlate with all cause mortality.They investigated the relationship between C reactive protein (CRP) and RDW postulating that somehow inflammation was involved but that did not seem to be the case.

How long will it take for the JUPITER data be dredged to see if statins ( at least rosuvastatin) can lower the RDW?